The autonomic nervous system in anorexia nervosa - an implication for the fat tissue.

Eating disorders are a heterogeneous group of diseases affecting mainly young people in developed countries. Among them, anorexia nervosa (AN) is the one with the highest mortality, up to five times higher compared to healthy individuals. The etiology of this medical condition is complex and still un- certain. However, disturbances of the autonomic nervous system (ANS) and increased lipolysis resulting in a decrease of the adipose tissue volume are common findings among AN patients. Since ANS is directly connected to adipocyte tissue, thus significantly affecting the body's metabolic homeostasis, we suspect that this relationship may be a potential pathophysiological underpinning for the development of AN. In this narrative review, we have analyzed scientific reports on ANS activity in AN considering different phases of the disease in humans as well as animal models. Due to the different effects of the disease itself on the ANS as well as specific variations within animal models, the common feature seems to be dysregulation of its function without the identification of one universal pattern. Nonetheless, higher norepinephrine concentrations have been reported in adipocyte tissue, suggesting local dominance of the sym- pathetic nervous system. Further studies should explore in depth the modulation of sympathetic in adipose tissue factor and help answer key questions that arise during this brief narrative review.